At present, the measuring devices installed in the service stations comprise a trasducer which transforms the fuel flow supplied into revolutions of a shaft connected with an encoder device (hereinafter called "pulser"). The pulser transforms the number of revolutions into a number of pulses which are subsequently counted by a suitable electronic device (hereinafter called "electronic head") and then transmitted to an electronic display which shows the numeric value corresponding to the quantity of the fuel supplied.
For fiscal reasons, such measuring devices are subjected to certifications and approvals and have to be sealed so that they are tamperproof to avoid any fraudolent modifications of the measurement.
In practice, known measuring devices have several weak points from the point of view of possible tampering with the measurements and which can occur in the ways that follow:
modification of the pulser disk: increasing the index points number, which relates to a certain number of disk revolutions, thereby increasing the number of pulses and causing a higher numeric value to be visualized by the display; PA1 a pulse multiplier can be inserted in the transmission line between the pulser and the electronic head; PA1 the software of the electronic head can be modified; PA1 the software of the display or the data thereto transmitted by the electronic head can be modified; PA1 the electronic equipment can be replaced.
Such cares of tampering are furthermore facilitated due to the technical difficulty of detecting them. This difficulty is often hard to overcome for the control officers.